1. Insititute of Electro-Optical Engineering, Tatung University, No. 40, Sec. 3, Zhongshan N. Rd., Taipei 10452, Taiwan
2. Department of Mechanical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan
3. Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan